With the development of cloud computing technology, applying cloud computing technologies in data centers has become an inevitable trend. Compared with those in a conventional data center, access requirements and interaction traffic between resource servers (such as servers, storage devices, database hosts, etc.) in a cloud computing data center will significantly increase. This means traffic patterns will change from mainly vertical (i.e., north-to-south traffic, specifically the traffic of users accessing servers) to mainly horizontal (i.e., east-to-west traffic, specifically the traffic between servers).
Currently, to cope with the sharp increase of the east-to-west traffic in a data center, many manufacturers proposed various solutions, and one type of the solutions is shown in FIG. 1. Based on a standard network communications protocol, when a physical machine or a virtual machine in a subnet (sub-network) 1 needs to communicate with another physical machine or another virtual machine in a subnet 2, all packets need to pass through a physical gateway or virtual gateway (i.e. a level-3 router). In this solution, all data packets that communicate across subnets need to pass through the physical gateway or virtual gateway. The physical gateway or virtual gateway becomes a bottleneck for the east-to-west traffic of the data center, and a total bandwidth of the east-to-west traffic of the entire data center is limited by the physical gateway or virtual gateway. In addition, due to the limited communications bandwidth of the physical gateway or virtual gateway, as the increase of concurrent communications, communications pairs preempt the communications bandwidth of the physical gateway from each other, resulting in a sharp drop of average network bandwidth.